scotland



NiTE STATES PATENT union.

JOHN STEWART MAOARTHUR, OF POLLOKSHIELDS, SCOTLAND, ASSIGNOR TO THE GOLD AND SILVER EXTRACTION COMPANY OF AMERICA, LIMITED,

OF GLASGOW, SCOTLAND.

PRECIPITATING PRECIOUS METALS FROM SOLUTIONS.

SPECIFICATION forming part of Letters Patent No. 592,153, dated October 19, 1897.

Application filed August 7,1894. Renewed September 5, 1896. Serial No. 605,031. (No specimens.)

Patented in England April 24, 1894,No. 8,184; inVictoria July 10, 1894, No. 11,497; in New South Wales July 12, 1894,110. 5,171; in Queensland July 14, 1894, No. 2,695 in Tasmania July 16,1894, No. 1,299; in New Zealand J ly 23,1894,No.6,987; in South African Republic August 7, 1894, No. 684; in Brazil A g st 28, 1894, No. 1,743; in Canada October 8, 1894, No. 47,145; in South Australia January 2, 1895, No. 2,846; in India January 11, 1895,No. 193; in Western Australia July 10,1895, No. 701; in Chile November 21, 1895, and in Mexico November 10,1896,No. 925.

To aZZ whom it may concern.-

Be it known that I, JOHN STEWART MAC- ARTHUR, asubject of the Queen of Great Britain, residing at 12 Knowe Terrace, Pollokshields, in the county of Renfrew, Scotland,

have invented certain new and useful Im- 15 ary 2, 1895; in New South Wales, No. 5,171,

' dated July 12, 1894; in New Zealand, No. 6,987, dated July 23, 1894; in Western Australia, No. 701, dated July 10, 1895; in Canada, No. 47,145, dated October 3, 1894; in India, No. 193, of 1894, dated January 11, 1895; in Chile, dated November 21, 1895; in Brazil, No. 1,743, dated August 28, 1894; in Mexico, No. 925, dated November 10, 1896, and in South African Republic, No. 684, dated Angust 7,1894;) and I do hereby declare that thefollowing is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it appertains to make and use the same.

0 My said invention has for its object to obtain increased economy in precipitating prec ious metals from cyanid or similar solutions, and to obviate injurious or impeding actions due to the presence of certain metals in the 3 5 solution.

In carrying out my invention I employ either zinc or aluminium as the precipitant for the precious metals, but when copper is present in the solution along with gold or sil- 4o ver or both it is precipitated first on the zinc or aluminium in a manner to interfere with the precipitation of the other metals. The copper seems to be. precipitated on the zinc or aluminium in a dense continuous form and 5 greatly impedes the contact between the liquid and the zinc or aluminium. To overcome this difficulty, I coat the zinc or aluminium with a porous precipitate of metallic lead, which prevents the impeding action of the copper. The porous lead may be deposited on the zinc or aluminium either before or during the precipitation of the other metals. It may be conveniently done by immersing the zinc or aluminium for about a minute in a solution containing about one per cent. of lead, as an acetate of lead, or as a plumbate or other suitable salt, or if done during the precipitation of the other metals a small quantity of the lead salt is added to the solution.

In cases in which the cyanid solution contains mercury along with gold or silver or both, the mercury is precipitated with the other metals, and although not impeding the chemical action is inconvenient physically, as it forms an amalgam, rendering it difficult to separate the gold and silver from the precipitating metal by chemical or mechanical means. To remove the mercury from the solution, I apply metallic lead, preferably in the form of shot or finely divided. The mercury and possibly a little silver become precipitated on the lead, and the precipitation of the gold and remainder of the silver proceeds without inconvenience.

In, ordinary solutions containing little else than gold and silver the zinc or aluminium is economized and the action facilitated by means of lead, preferably in the form of shot or finely divided, the gold and silver being deposited on the lead as well as on the zinc or aluminium. It is the action of the lead when in direct or indirect contact or connection with the .zinc or aluminium which is advantageous, the action of lead alone being un- 8'5 satisfactory. v

The lead is not used as a precipitating agent, but is used to protect the precipitant-that is to say, it simply modifies the action of the precipitating agent by coating it with porous 9o lead, which is in itself chemically inertthat is, the porous lead is not acted on chemically by the solution in which it is immersed, but acts merely as a physical basis for the deposition of the precious metals.

I wish it to be understood that I do not claim the use of either zinc or aluminium per so as a precipitant, but only the use of same in connection with lead.

Instead of lead any suitable chemically inert substance which is a good conductor and negative to zinc or aluminium maybe used such, for example, as tin, iron, or carbon. I believe, however, that lead will be found most convenient in practice.

Having fully described my invention, what I claim, and desire to secure by Letters Patent, is-

1. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant protected by a metal inert in said solution.

2. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant protected by a coating of lead.

3. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant protected by finely-divided particles of lead.

4. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant composed of zinc protected by a metal inert in said solution.

5. The process of precipitating a precious metal from a cyanid solution which consists in subjecting said solution containing a base metal to the action of a precipitant protected by lead.

0. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant composed of zinc protected by a coating of lead.

7. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant composed of zinc protected by finely-divided particles of lead.

8. The process of precipitating a precious metal from a cyanid solution which consists in subjecting said solution containing a base metal. to the action of a precipitant composed of Zinc protected by lead.

9. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal, such as mercury or copper to the action of a precipitant protected by lead.

10. The process of precipitating a precious metal from a cyanid solution, which consists in subjecting said solution containing a base metal to the action of a precipitant protected by metallic lead, substantially as described.

11. The process of precipitating a precious metal from a cyanid solution containing copper, which consists in subjecting said solution to the action of a precipitant protected by metallic lead so as to insure perfect contact between the lead and the solution and thereby remove the copper prior to the precipitation of the precious metal.

JOHN STINVART MACAR'IIIUR.

Witnesses:

Cnas. A. ALLISON, Gno. A. ANDERSON. 

